1. Field of the Invention
The present invention relates to a wireless transceiver, and more particularly to a wireless transceiver supporting a multi-mode/multi-band.
2. Description of the Related Art
Generally, countries all over the world employ different communication schemes for mobile communication services and each of mobile communication schemes uses various frequency bands.
The mobile communication schemes include, for example, a Code Division Multiple Access (CDMA) scheme, a Global System for Mobile (GSM) communication scheme, a General Packet Radio Service (GPRS) scheme, an Enhanced Data rates for GSM Evolution (EDGE) scheme, a Wide band Code Division Multiple Access (WCDMA) scheme, etc. in each country. The CDMA scheme uses frequency bands of 800 MHz, 1800 MHz and 1900 MHz. The GSM scheme uses frequency bands of 850 MHz, 900 MHz, 1800 MHz and 1900 MHz. The WCDMA scheme includes frequency bands of 850 MHz, 1900 MHz and 2000 MHz.
Previous wireless mobile stations have been manufactured to use signals of one or two frequency bands adapted to a specific communication service, to which a user has subscribed, among every mobile communication services. Thus, the mobile stations can only use one or two mobile communication services, among the various mobile communication services, which are used in a specific country. Therefore, when a user travels or makes a business trip to a region in which a communication service is different from that of his/her country, the use cannot use a mobile station of the region, which provides inconvenience for the user.
Thus, the user requires a mobile station capable of receiving the mobile communication service of all countries. Further, manufacturers of the mobile station need to manufacture a mobile station through which the user can use the mobile communication service in all the countries according to the user's requirement. In order to use all the mobile communication services that exist in a given country, there exists a need for a mobile station supporting multi-mode and multi-band. A term “multi-mode” means a Frequency Division Duplex (FDD) mode based on a WCDMA scheme, a Time Division Duplex (TDD) mode based on a GSM scheme, etc., while a term “multi-band” refers to different frequency bands.
It is possible to consider a multi-mode/multi-band wireless transceiver having a construction as shown in FIG. 1.
FIG. 1 shows a multi-mode/multi-band wireless transceiver, which supports two modes (i.e. the FDD mode and TDD mode), supports three service bands including WCDMA 2000, WCDMA 1900, and WCDMA 850 in the FDD mode, and supports four service bands including Personal Communication Service (PCS) 1900, Digital Cellular System (DCS) 1800, GSM 900, and GSM 850 in the TDD mode. In WCDMA 2000, WCDMA 1900, WCDMA 850, PCS 1900, DCS 1800, GSM 900 and GSM 850, the numbers 2000, 1900, 1800 and 850 represent the frequency bands of 2000 MHz, 1900 MHz, 1800 MHz and 850 MHz, respectively.
WCDMA 2000, WCDMA 1900 and WCDMA 850 respectively indicate the frequency bands of 2000 MHz, 1900 MHz and 850 MHz in the WCDMA scheme. PCS 1900, DCS 1800, GSM 900 and GSM 850 respectively indicate the frequency bands of 1900 MHz, 1800 MHz, 900 MHz and 850 MHz.
Referring to FIG. 1, an antenna 104 is selectively connected by means of a switch 106 to one of duplexers 108, 110 and 112, and a Transmitting/Receiving (T/R) switch 156. The duplexers 108, 110 and 112 separate transmitting and receiving signals of three frequency bands of WCDMA 2000, WCDMA 1900, and WCDMA 850 in the FDD mode, respectively. The T/R switch 156 switches transmission and reception relating to the frequency bands of PCS 1900, DCS 1800, GSM 900, and GSM 850.
An operation of the multi-mode/multi band wireless transceiver, in which a current service frequency band is one of the WCDMA 2000, WCDMA 1900, and WCDMA 850, and which operates in the FDD mode with relation to a reception of signal, will be described with reference to FIG. 1. Received signals introduced from the antenna 104 to the switch 106 are applied to one, which corresponds to the current service frequency band, of Low Noise Amplifiers (LNA) 114, 116 and 118 of a Radio Frequency Integrated Circuit (RFIC) 102 and amplified through one, which corresponds to the current service frequency band of the WCDMA 2000, WCDMA 1900 and WCDMA 850, of the duplexers 108, 110 and 112. The received signal amplified by each LNA 114, 116 or 118 is input to a Radio Frequency (RF) receiving portion 126 through each Radio Frequency Surface Acoustic Wave (RF SAW) filter 120, 122, or 124 which is installed outside the RFIC 102, and is converted into a baseband signal by the RF receiving portion 126, which is finally provided to a baseband processing unit 100. The baseband processing unit 100 functions as a modem for mobile communication in the case where the multi-mode/multi-band wireless transceiver is employed in a mobile station.
An operation of the multi-mode/multi band wireless transceiver, in which a current service frequency band is one of the WCDMA 2000, WCDMA 1900, and WCDMA 850, and which operates in the FDD mode with relation to a transmission of signal, will also be described with reference to FIG. 1. A baseband signal transmitted from the baseband processing unit 100 to a RF transmitting portion 128 is converted to an RF signal and then is pre-power-amplified by one, which corresponds to the current service band, of Pre-Power Amplifiers (PPA) 130, 132 and 134. The transmitted signal pre-power amplified by each PPA 130, 132, or 134 passes through one, which corresponds to the current service frequency band, of Band Pass Filters (BPF) 136, 138 and 140 and is power-amplified by each Power Amplifier (PA) 142, 144, or 146, which in turn is applied to a switch 106 through one, which corresponds to the current service frequency band, of the duplexers 108, 110 and 112. Then, the signal is transmitted by way of the switch 106 and the antenna 104.
An operation of the multi-mode/multi band wireless transceiver in which a current service frequency band is one of the PCS 1900, DCS 1800, GSM 900 and GSM 850 and which operates in the TDD mode, with relation to a reception of signal, will also be described with reference to FIG. 1. A signal introduced from the antenna 104 to the switch 106 passes through the T/R switch 156 of a PA module 154 and one, which corresponds to the current service frequency band, of BPFs 162, 164, 166 and 168 and then is applied to one, which corresponds to the current service frequency band, of the LNAs 170, 172, 174 and 176 of the RFIC 102. The signal amplified by each LNA 170, 172, 174 or 176 is input in a RF receiving portion 178 and converted into a baseband signal by means of the RF receiving portion 178. Then, the signal is provided to the baseband processing unit 100.
An operation of the multi-mode/multi band wireless transceiver in which a current service frequency band is one of the PCS 1900, DCS 1800, GSM 900 and GSM 850 and which operates in the TDD mode, with relation to a transmission of signal, will also be described with reference to FIG. 1. The baseband signal is transmitted from the baseband processing unit 100 to the RF transmitting portion 148 and then converted into a RF signal by means of the RF transmitting portion 148. Then, the RF signal is pre-power-amplified by one PPA 150 or 152 corresponding to the current service frequency band. After being power-amplified by PA 158 or 160 of the PA module 154, the amplified signal is applied to the switch 106 by way of the T/R switch 156. Finally, the amplified signal is transmitted through the switch 106 and the antenna 104.
The multi-mode/multi-band wireless transceiver constructed as shown in FIG. 1 employs a separate duplexer for each service mode or each service band in the FDD mode. This is necessary because the transceiver uses a duplexer having a fixed band for transmission/reception filtering.
Further, a separate RF SAW filter through which the service frequency band passes must be adapted to each service mode or each service band. The reason for this is because the transmitting and receiving filter of the duplexer is a band filter. The main reason for using the RF SAW filter is to decrease an interference of the transmission signal with the signal receiving band in the FDD mode.
However, since the duplexer, or SAW filter, is a band pass filter which passes the service band, it is not helpful to improve an in-band blocking characteristic or to relieve Input 3rd Order Intercept Point (IIP3) and Input 2nd Order Intercept Point (IIP2) characteristics of a mixer which converts the received signal into a low band in the RF receiving portion. Thus, it is difficult to relax a specification of the RF system.
Further, since a separate duplexer and the RF SAW filter are used in every service mode or in every frequency band, respectively, they are a burden to the transceiver in view of cost, volume and required mounting area. Specially, an active element tends to have a gradually smaller size as circuit technology has been developed. However, since an inactive element, such as RF SAW filter, still does not have a small size, it is a burden to the transceiver.
In the case of supporting all the different service modes, such as FDD and TDD, since a duplexer for the FDD mode and a T/R switch for T/R switching must be separately used in the transceiver, they are a burden to the transceiver in view of cost, volume and required mounting area of the transceiver.